Electrical elements of integrated circuits are formed in a series of processes applied to a semiconductor wafer. After completion of wafer level manufacturing the semiconductor wafer is separated into individual semiconductor dies. Die separation, also called “dicing”, may include attaching a carrier substrate at one side of the semiconductor wafer. The carrier substrate holds the wafer in place during dicing, which may include scribing, sawing, and/or etching, by way of example. Conventional laser dicing methods use laser light at a wavelength that is absorbed by the semiconductor material of the semiconductor wafer. Stealth dicing uses laser light with a wavelength at which the semiconductor substrate is highly transparent such that the laser beam can be focused inside the semiconductor wafer. Around the focal point the laser beam melts the semiconductor material, which recrystallizes in polycrystalline form with high density dislocations that result in significant mechanical stress. The mechanical stress effects that perpendicular cracks can develop towards the wafer front and back surfaces. In this way the stress induced by local transformation of the single-crystal semiconductor material into polycrystalline semiconductor material facilitates die separation by applying an external force in a suitable way.
Mechanical dicing is easy to implement and allows high throughput but tends to generate cracks that may propagate into the semiconductor devices. The cracks are hardly to detect but may have significant impact on device reliability. There is a need for a method for die separation with improved trade-off between cost and device reliability.